Heater



FIG. 1 is a front view;

FIG. 2 is a rear view;

FIG. 3 is a right side view;

FIG. 4 is a left side view;

FIG. 5 is a top view;

FIG. 6 is a bottom view; and,

FIG. 7 is a perspective view.

The broken lines depict environment and form no part of the claimed design. 

CLAIM The ornamental design for a heater, as shown and described. 